An Evaluation of the Protection Framework of Prepulse Inhibition (2011)

Undergraduates: Collyn Murray, Joseph C. Franklin

Faculty Advisor: Mitch Prinstein
Department: Psychology & Neuroscience

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Although prepulse inhibition (PPI) of the acoustic startle response has become a prevalent measure in both basic and applied psychophysiological research, the theoretical foundation of this measure has never been empirically validated. This longstanding framework, Graham’s protection theory of PPI (1975), states that the function of PPI is to protect the processing of the prepulse from interruption by the subsequent startle stimulus. Conversely, research on stimulus processing provides evidence for a potential alternative hypothesis: PPI is a function of the actual processing of the prepulse (Franklin et al., in progress). The aims of the present study were to (1) provide the first direct test of Graham’s protection theory, and (2) to test for and evaluate evidence supporting the alternative hypothesis. PPI, in conditions varying by startle stimulus intensity and prepulse intensity, and a prepulse tone discrimination task were used as measures of stimulus processing (N = 39). Neither the physiological data nor tone discrimination analyses provided evidence for Graham’s protection theory. That PPI increased with increased prepulse intensity provides evidence for the alternative hypothesis and is consistent with previous findings (e.g., Blumenthal et al., 2006; Franklin et al., 2007). Tone discrimination accuracy further followed trends predicted by the alternative hypothesis. These findings indicate that further evaluation of the protection theory is necessary.